Cyclone Tracy was the second cyclone predicted to hit Darwin, Australia in December 1974 (Cyclone Selma was the first but never reached the city). The dissipation of Cyclone Selma prior to landfall caused many residents to disregard warnings about Tracy. Unfortunately, this would only contribute to Cyclone Tracy becoming the deadliest tropical cyclone in Australian history.
The cyclone developed from a tropical low in the Arafura Sea (between Australia and New Guinea) on December 20, 1974, about 500 km (300 miles) northeast of Darwin in Australia’s Northern Territory. By the evening of 21 December, the Darwin meteorological office received an infrared satellite image from the National Oceanic and Atmospheric Administration's (NOAA’s) satellite, NOAA-4, showing that the system had further developed and spiraling clouds could be observed. By 9 PM on 21 December the storm was officially pronounced a tropical cyclone, located 200 kilometers (124 miles) north northeast of Cape Don, Australia. Over the next few days, the cyclone moved in a southwesterly direction, passing north of Darwin on 22 December. Winds gusted to 120 km/h (75 mph) as the storm continued to travel south southwestward at 9 km/h (5.6 mph). Early on 23 December, Tracy’s forward movement slowed to a mere 6.4 km/h (4 mph) as the system rounded the western tip of Bathurst Island and moved over the Timor Sea. The shallow coastal waters of the Timor Sea (less than 59 m [160 ft] deep) were uniformly warm from the ocean surface to the ocean floor. With no cold water to upwell from depth, the slow-moving Tracy quickly intensified. By 24 December, Christmas Eve, it became apparent that the cyclone would not just pass by the city of Darwin, but rather go directly over it. Just after midnight, on Christmas Day, the storm made landfall in Darwin as a Category 4 cyclone on the Australian cyclone intensity scale (Category 3 on the Saffir-Simpson Hurricane Wind Scale). Peaks winds of 217 km/h (135 mph) winds were recorded at the Darwin Airport just before the airport’s anemometer blew away. A storm surge of 4 m (13 ft) occurred off the coast of Darwin as Tracy passed, but it did not cause additional flood damage, as the tide was low at that time.
On the day of the cyclone, most residents of Darwin believed the cyclone posed no threat to the city. Cyclone Selma had been predicted to hit Darwin earlier that month, but it instead tracked north and did not impact the area. Despite several warnings, the people of Darwin did not evacuate or prepare for the cyclone and many residents continued with their Christmas festivities. Moreover, due to the cyclone’s small diameter, gale force winds only extended 40km (25 miles) from the storm center, not yet reaching gale force in Darwin on Christmas Eve. Winds accelerated from a breeze to gale force over a short, 5-hour period, and Cyclone Tracy took many of the residents of Darwin by surprise. The storm caused significant damage, destroying 80% of the buildings in the city. It also claimed 71 lives, injured 650, left 41,000 homeless, and caused 35,362 people (of the 47,000 total population of Darwin) to evacuate. The total cost of the storm is estimated to have been $837 million (1974 AUD) or $586 million (1974 USD).
Divine Wind: The History and Science of Hurricanes
Northern Territory Library